> After referring to this post (https://afni.nimh.nih.gov/afni/community/board/read.php?1,76015,76017#msg-76017),
> the numerator and denominator should be 4 and 88 respectively right?

Yes, that's correct.

> The first 4 should be the code for statistics, which is F-stats. But how about 0? What does it mean?

I'm not sure what the 0 is about, but it's not important to know in the current context. A couple of more ways to find degrees of freedom:

[sscc.nimh.nih.gov]

> I then run 3dcalc -a myFile+tlrc'[##]' -expr 'fizt_p2t(fift_t2p(a,N1,N2))' -prefix outputFileName as you suggested.
> The idea is to first convert f-stats to p value? and then convert p value to z-stats right?

Yes, that's right.

Gang